Heart Rate Variability a Good Intensity Measure

Tracking intensity levels is a great way for athletes to ensure they are getting the most out of their training. If you’re hitting the gym and tracking your progress this is pretty easy to do, but if you’re doing a more complex activity like gymnastics or MMA, determining how hard you’re going on any given day can be a lot more challenging. Along with that challenge, you find athletes slipping into overtraining more often than they’d like.

While lab equipment might work well for assessing training session intensity, most of us don’t have regular access to it. For precise measurements, it has been hypothesized that heart rate variability, or HRV, can be a useful measurement tool. In a recent study in the Journal of Strength and Conditioning Research, researchers took on the challenge to discover how effective this tool might be.

HRV itself can be hard to wrap your head around. Essentially, it is the change in length of time between heartbeats. Because the body tracks many factors that influence heart rate, there is a natural variability between each heartbeat. The activation or suppression of different parts of your nervous system can actually change this level of variability. Greater stimulation of the nervous system will often decrease HRV, which means the time in between heartbeats won’t change as much from beat to beat.

There are a few simpler methods of measuring intensity that are also easy to perform. For example, the rate of perceived exertion, or RPE, is simply a rating, usually on a scale from zero to ten, of workout intensity. Questionnaires have been developed as well, based on a similar concept as the RPE, but perhaps a little more comprehensive. The problem with these methods is they are based on subjective measures. The athletes themselves choose how intense a workout felt. This method has been shown to work, but might be less precise than HRV.

Thankfully, HRV can be measured by some heart rate monitors. In this study, the researchers studied young gymnasts and compared those using HRV heart rate monitors to those measured by RPE and questionnaire methods. The researchers found some strong correlations, despite their small sample size of only a few gymnasts. The HRV of the athletes while laying down the morning after a workout correlated with the perceived exertion taken the previous day. The difference between HRV taken while laying down and seated HRV the morning after a workout had an even stronger relationship to the perceived exertion, but not to the questionnaire method. The strongest correlations of all three methods were seen in the differences between the training day HRV and the HRV of the day after a workout.

This study suggests you should be able to properly assess the intensity level of your workouts if you have a monitor capable of reading HRV. If you track HRV over time you can eventually determine your limits. Knowing your limits will allow you to work within them and avoid overtraining syndrome.

The study is limited insofar as it seeks a stable method of measuring intensity, but uses subjective methods as a point of comparison. Not the best study design it seems. However, since those subjective methods themselves are pretty dependable, you may want to start marking down your HRV from day to day as a good insurance policy against overtraining.